1. Field of the Invention
The present invention concerns a hot melt ink used in an ink jet recording device and, more in particular, it relates to a hot melt ink used in a hot melt type ink jet recording device in which recording is conducted by heat fusion of ink in a state of a temperature higher than a room temperature.
2. Description of Related Art
As the ink jet recording system, there have been proposed various kinds of systems, for example, a so-called electric field control system of jetting out ink by utilizing an electrostatic attraction force; a so-called drop-on-demand system of jetting out ink by utilizing a vibrational pressure of a piezo element (pressure pulse system); and a so-called thermal ink jet system of jetting out ink by utilizing a pressure resulting from forming and growing bubbles by heating at high temperatures, and they can provide images of extremely high fineness.
For the ink jet systems described above, an aqueous ink using water as a main solvent and an oil ink using an organic solvent as a main solvent have generally been used. Printed images obtained by using the aqueous ink are generally poor in water proofing, whereas the oil ink can provide printed images of excellent waterproofing.
However, since the aqueous and oil inks are liquid at room temperatures, they tend to cause blurring when they are printed on recording paper and cannot obtain a sufficient printing density. Further, they often form depositions from the ink since they are liquid, which causes remarkable deterioration of the reliability in the ink jet recording system.
With an aim of improving the drawbacks of the solvent type inks in the prior art, an oil ink for so-called hot melt type ink jet recording using ink which is solid at normal room temperatures (i.e., about 18.degree. C. to about 27.degree. C.) has been proposed. Specifically, there have been proposed ink containing a dialkyl sebacate in the specification of U.S. Pat. No. 3,653,932, ink containing a natural wax in the specification of U.S. Pat. No. 4,390,369 (Japanese patent Laid-Open No. Sho 58-108271), ink containing a stearic acid in the specification of U.S. Pat. No. 4,758,276 (Japanese Patent Laid-Open No. Sho 59-22973), ink containing acid or alcohol of 20 to 24 carbon atoms and, further, containing therewith ketone of a relatively higher melting point in the specification of U.S. Pat. No. 4,659,383 (Japanese Patent Laid-Open No. Sho 61-83268), ink containing a thermoserring resin having a high hydroxyl value, a solid organic solvent containing a melting point lower than 150.degree. C. and a small amount of a dye substance in the specification of U.S. Pat. No. 4,820,346 (Japanese Patent Laid-Open No. Sho 62-48774), ink comprising a colorant, a first solvent which is solid at a room temperature and liquefied when heated to a temperature higher than the room temperature and a second solvent which is liquid at the room temperature and highly evaporizing for dissolving the first solvent in the specification of U.S. Pat. Nos. 5,000,786 and 5,124,719 (Japanese Patent Laid-Open No. Hei 2-167373), ink containing synthetic wax having a polar group and a dye soluble to the wax in Japanese Patent Laid-Open No. Sho 62-295973.
However, the hot melt inks described above have no concern with considerations such as for sufficient reduction of heat of fusion of inks, sufficient improvement of transparency, prevention of releasability due to flexing of printed matters by providing plasticity, provision of sufficient luster and sufficient dissolution of dyes.